Process of decarburizing iron or steel or their alloys



Patented Sept. 1, 1931 UNITED STATES PATENT OFFICE WALTER SCHOTTKY, OF BERLIN-CHARLOTTENBUBG, GERMANY, ASSIGNOR TO SIEMENS & HALSKE AKTIENGESELLSCHAFT,'OF SIEMENSSTADT, NEAR BERLIN, GERMANY, A

CORPORATION OF GERMANY PROCESS OE DECARBURIZIN G IRON OR STEEL OB THEIR ALLOYS No Drawing. Application filed June 25, 1929, Serial No. 873,693, and in Germany J'une27,

My invention relates to improvements in the decarburization of iron and steel and their alloys.

gen prevails and the walls The decarburization of iron and steel and their alloys is generally carried out by bringing these materials in the melted or the red hot state in contact with oxygen or an oxygen containing gas mixture and thus oxidizing the carbon. It is also well known in the art that a number of other gases and gas mixtures, more particularly steam, carbon monoxide or hydrogen as well as a gas mixture designated as blast furnace gas and consisting mainly of nitrogen and carbon monoxide are suitable for the decarburization process, more particularly for edge decarburization.

On the other hand the fact is well known in the art that a carbon content above 0.008 p. c. is sufiicient to exert a detrimental effect upon the magnetic properties of the iron, and in particular increases the hysteresis losses. None of the at present known decarburization processes renders it possible to go below this limit, however.

According to my invention this end in view is attained by heating to temperatures corresponding at least to red heat (and therefore including melting temperatures) the iron or steel or their alloys to be decarburized in an atmosphere of hydrogen under application of pressures, which are of the order of 100 atmospheres. Preferably my improved process is carried out at a temperature of at least 1000 centigrade (1800 Fahrenheit), in order to speed up the process. The decarburization process may, for instance, be carried out in a chamber in whicha constant high pressure of hydroof which are kept at a lowtemperature. To generate the heat necessary for carrying out my improved process the iron tobe decarburized is heated in a crucible ofceramic material either by high frequency or by, electric resistance heating. In many cases it is advisable to blow the hydrogen prior art. p I claim as my invention:

of iron until the carbon content has dropped sufficiently, and to remove the methane mainly forming during the treatment, by selective absorption media, by decomposition at high temperature and lower'pressure, or by freezing it out. If my improved process is applied to red hot iron, the iron is preferably employed in the form of thin pieces, such as sheets, strips or wires, in order to obtain a thorough decarburization up to the desired limit. After the termination of the processthe hydrogen is preferably first withdrawn by a suction pump and the chamber evacuated in which is contained the decarburized iron. The iron is then heated to a high tem erature to expel any occluded hydrogen. The cooling down of the iron after the application of'my proved process is preferabl carried out in a vacuum. If molten iron as been treated the iron is preferably cast into moulds under exclusion of air. The charges should be as large as possible, since the loss of heat is then lower. The hydrogen may, if desired, be" preheated before bringing it in contact with the iron to be decarburized.

According to myimproved process it is possiblein a comparatively short time to obtain chemically pure iron, if desired,

without losses of iron or any constituents of the alloy, which frequently occur in the known processes. If pure hydrogen is employed in my process no scale is formed on the iron.

Various modifications and changes may be made without departing from the spirit and the scope of the invention, and I desire, therefore, that only such limitations shall be placed thereon asare imposed by the 1. In a process of decarburizing iron "or steel or their alloys by heating'to temperatures corresponding at least to red heat in .an atmosphere of hydrogen, the application of a pressure in the treatment chamber of the order of atmospheres.

2. In a process of" decarburizing iron or steel or their alloys in an atmosphere 'of hydrogen, the application of a pressure of the order of 100 atmospheres and of a heating temperature of'over 1000 centigrade.

3. In a process of decarburizing iron or steel or their alloys by heating to temperatures corresponding at least to red heat 1n an atmosphere of; hydrogen, the application in the treatment chamber of a pressure of the order of 100 atmospheres, the walls of the treatment chamber being kept at a low temperature.

4. In a process of decarburizing iron or steel or their alloys by heating to temperatures corresponding at least to red heat in an atmosphere of hydrogen, the application of high frequency current for heating the material to be treated and of a pressure of the order of 100 atmospheres in the treatment chamber.

5. In a process of decarburizingiron or steel or their alloys by heating to temperatures corresponding at least to red heat in an atmosphere of hydrogen, the application of an airtight crucible of a material containing no carbon and a pressure of the order of 100 atmospheres in said crucible.

6. In a process of decarburizing iron or steel or their alloys by heating to temperatures corresponding an atmosphere of hydrogen. the application in the treatment chamber during the decarburization process of a of 100 atmospheres, withdrawn by a suction pump after the decarburization is finished and the decarburized iron being heated to a high temperature in a vacuum.

7. In a process of decarburizing iron or the hydrogen being steel or their alloys by heating to temperatures corresponding at least to red heat in an atmosphere of hydrogen, the application in the treatment chamber during the decarburization process of a pressure of the order of 100 atmospheres, the hydrogen being withdrawn by a suction pump after the decarburization is finished and the decarburized iron being heated to a high temperature in avacuum and also cooled in a vacuum.

8. The process of treating iron or eel or their alloys, which consists in decarburizmg them by heating the metal to temperatures corresponding at least to red heat in an atmosphere of hydrogen under a pressure of the order of 100 atmospheres, then removing the hydrogen by suction, and thereupon heating the decarburized metal to a high temperature in a vacuum.

9. The process of treating iron or steel or their alloys, which consists in decarburizing them byheating the metal to temperatures corresponding at least to red heat in an atmosphere of hydrogen under a pressure of the order of 100 atmospheres, then removing the hydrogen by suction, and thereupon pressure of the order heating the decarburized metal to a high temperature in a cooling In testimony w .vacuum and subsequently such metal in a vacuum.

hereof I affix my signature.

WALTER SCHOTTKY.

at least to red heat in 

